<title>555 Pulse Width Modulator</title>
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<param name=startCircuit value="555pulsemod.txt">
<param name=startLabel   value="555 Pulse Width Modulator">
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<p>
This circuit encodes a voltage with
<a
href="http://en.wikipedia.org/wiki/Pulse-width_modulation">pulse-width
modulation</a> using a
<a href="http://en.wikipedia.org/wiki/555_timer_IC">555 timer
chip</a>.  The width of the output pulses varies depending on
a control voltage.
<p>
The width of the pulses is set by a <a href="http://en.wikipedia.org/wiki/Triangle_wave">triangle wave</a> oscillator connected
to the "ctl" input of the 555.  The rest of the circuit is just like
the <a href="e-555square.html">square wave oscillator</a>.  By
applying a voltage to the "ctl" input (normally 2/3 V<sub>in</sub>),
we can control the voltage
which ends a timing interval.  When the "th" input reaches this
value, the output goes low.  So the 555 will oscillate faster when the
ctl input is lower.

<p>
Next: <a href="e-555schmitt.html">555 Schmitt Trigger (inverting)</a><br>
Previous: <a href="e-555sequencer.html">555 Pulse Sequencer</a><br>
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<br>Generated Tue Dec  7 2010
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